The present invention relates to a method of and apparatus for controlling the light output of a printing lamp used in a photographic printer.
To make photographic prints having proper density and color balance, a conventional photographic printer uses sensors to measure an original illuminated by a printing lamp to detect an amount of light passed through the original. Insertion of color correction filters into the optical path is regulated in accordance with the measured light values. The sensors include three sensors for photometry of average transmittance densities of red, green and blue colors, and an image sensor for photometry of the density at each point of the image. A color image sensor also is known which measures the densities of red, green and blue colors at each point of an image, the average transmittance density of each color then being calculated by using the densities at respective points.
The light emission quantity of a printing lamp generally is determined based on an exposure time sensor sensitivities and the like. A halogen lamp used as the printing lamp normally is excited at about AC 65 V r.m.s. Conventionally, an operator manually turns a voltage adjustor while monitoring a voltage meter to obtain such a lamp voltage.
The light emission quantity varies with each printing lamp. In replacing a printing lamp with a new one, not only the lamp voltage setting but also the print condition setting (determining parameters of an exposure amount calculating equation) has been carried out in order to ensure the same finished print quality as that achieved with the old printing lamp. The conventional lamp replacement accompanying print condition setting thus has been troublesome and time consuming.